1. Field of the Invention
This invention relates to a photographic camera, and more particularly to a photographic camera to which a converter lens can be attached.
2. Description of the Prior Art
An automatic camera which has a built-in flash device and an automatic exposure controlling device operates automatically to cause the flash device to emit light when the brightness of an object to be photographed becomes low until the exposure of the camera exceeds, for example, a preset exposure value EV.
When a front tele-converter lens, including a conversion lens system, is attached to such camera, an entire focal length of a whole lens system comprising a main lens system provided in the camera and the conversion lens system is extended in comparison with the focal length of the main lens system alone. However, an opening diameter of the aperture diaphragm provided in the main lens system is not changed, and therefore, F-number of the whole lens system is not changed in comparison with the F-number of the main lens system alone, even if the front tele-converter lens is attached to such camera. Therefore, the possibility of taking a plurality of out-of-focus photographs will be increased if the front tele-converter is attached, since the depth of field of the whole lens system is narrower than that of the main lens system alone.
A lens shutter is known as an exemplary means for resolving the problem just described. The lens shutter is constructed to gradually open a plurality of shutter blades with decreasing its opening speed by a governor, and to start closing the plurality of shutter blades during its opening operation when the brightness of the object is sufficiently high. The plurality of shutter blades also serve as an aperture diaphragm in the above-described lens shutter. Therefore, the lens shutter enables photographing in a restricted aperture condition in which the depth of field is relatively wide to prevent taking of a plurality of out-of-focus photographs.
Such a camera as described above can be constructed such that, when the brightness of an object to be photographed is excessively low, a flash device of the camera is automatically activated to emit flash light. However, also a camera is already known which includes a switching means for switchably controlling a flash device so that, if a photographer desires so, the flash device may not emit light, that is, emission of light may be inhibited in order to attain a distinct photographing effect. Even with the camera just mentioned, where no converter lens is used, the shutter speed is not lowered considerably, and accordingly, out-of-focus photographing takes place little.
However, in order to photograph using a converter lens but without using a flash device when an object to be photographed is too dark, the shutter speed must necessarily be decreased. Even with the lens shutter, however, there is a drawback that, as the shutter speed decreases, the period of time within which the aperture diaphragm is open increases and a small aperture restricting effect by the lens shutter is lost, resulting in increase in probability of out-of-focus photographing.
Meanwhile, an exemplary tele-converter is secured at a bottom portion thereof to a bottom portion of a camera and includes an auxiliary lens system which is mounted for moving between an operative position and an inoperative position with respect to a main lens system of the camera by means of a hinge provided in the tele-converter lens.
Further, a camera is already known which includes a switch located at a top portion thereof such that it may be pushed by a projection provided at an upper portion of a tele-converter to detect that the tele-converter is not in its inoperative position but is in its operative position.
Where the detecting switch is exposed outside the camera as in a conventional camera, there are drawbacks that dust or the like is accumulated on or around the switch and may cause incomplete contact of the switch and that the switch may be depressed inadvertently or in error.